Environmental Pollution 57 (1989) 167-178 Metal Contamination of Drinking Water from Corrosion of Distribution Pipes Ibrahim A. Alam & Muhammad Sadiq Water Resources and Environment Division, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia (Received 24 February 1988; revised version received 22 September 1988; accepted 26 September 1988) A BS TRA C T The objectives of th& study were to evaluate metal contamination of drinking water resulting from the corrosion of distribution pipes and its significance to human health. A community in Dhahran, which is served from its own desalination facilities, was chosen for this study. About 150 drinking water samples were collected and analyzed for metal concentrations using an inductively coupled argon plasma analyzer. It wasjbund that copper, iron and zinc in the drinking water increased during its transportation from the desalination plant to the consumers. This increase was related to the length and material of distribution pipes. Concentrations of copper and zinc were increased during overnight storage of water in the appliances. Metal concentrations found in this study are discussed with reference to human health. INTRODUCTION Drinking water in Saudi Arabia is mainly obtained by desalting seawater or ground water. After desalination, the finished water is generally mixed with ground water, disinfected, pH adjusted, and transported through the distribution network to the consumers. Drinking water supplies contain variable amounts of metals (Bostrom & Wester, 1967; Durum, 1974; Andermann & Shapir, 1975). Several of these 167 Environ. Pollut. 0269-7491/89/$03'50 O 1989 Elsevier Science Publishers Ltd, England. Printed in Great Britain 168 lbrahim A. Alam, Muhammad Sadiq metals are essential for normal functioning of the human body, whereas others are non-essential (Underwood, 1971; WHO, 1973). Essential as well as non-essential metals can be toxic to humans if present above threshold levels (Baccini & Roberts, 1976). The sources of metals in-drinking water are associated either with natural processes or man's activities (NRC, 1977). Generally, desalination removes most of these metals (Andermann & Shapir, 1975). However, during mixing with ground water, disinfection, fluoridation, and pH adjustment, metals are reintroduced into the finished water. The occurrence of corrosion in the distribution system may also add metals to the finished water before it reaches the consumers (Semple et al., 1960; Harris & Elsea, 1967; Dangel, 1975; Moore et al., 1975). Therefore, corrosion of distribution pipes could be the major source of toxic metal contamination of drinking water supplies in Saudi Arabia. Information on the contribution of pipe corrosion to the concentrations of metals in the drinking water supplies is scanty. The objectives of this study were to investigate corrosion of the distribution pipes as a source of metal contamination, and to evaluate probable human health effects associated with the corrosion products in the drinking water. MATERIALS AND METHODS A population of over 4000 in Dhahran, Saudi Arabia, was selected for this study. The study area had three desalination plants which were supplied with raw water from nine groundwater wells within 1 km of the desalination facili- ties. The casings of the groundwater wells were of cast iron. Groundwater from these wells was transported through corrugated cement pipes to the storage tank. During treatment in the desalination facilities, a predetermined portion of the salt was removed from the groundwater. The desalinated water was chlorinated, using sodium hypochlorite, and pH was adjusted by adding soda ash. The desalinated and treated water was pumped through main distribution pipes to the inlet for each building. The type and material quality of the pipes within different buildings were variable. Information on the type of material, age, and length of the supply pipes of the mains, as well as from the main to the sampling points, is listed in Table 1. Similar information on faucets and appliances was not available. About 150 drinking water samples were collected from 32 randomly selected locations within the study area. To evaluate the effect of overnight storage in the faucets and appliances, 50 ml of water were taken before using drinking water early in the morning. This water sample was designated as SO. To have a uniform residence time, all the office and school locations were flushed for 20 min between 8 and 9 pm on the previous evening. The average Metal contamination of drinking water from pipe corrosion 169 TABLE 1 Type, Age and Size of Distribution Pipes in the Study Area S. no. Location Pipe age Main pipe Distribution pipe~ (year) Length Material Size Length Material Size (m) (em) (m) (em) 1 House 1978 1 900 A/C 10 20 Gav. iron 2"5 2 House 1979 1600 A/C 10 20 Gav. iron 2'5 3 House 1979 1 550 A/C 10 20 Gav. iron 2"5 4 House 1983 2390 A/C, PVC 10 20 PVC 2"5 5 House 1980 2000 A/C 10 20 PVC 2-5 6 House 1980 2 100 A/C 10 10 + 10 PVC, Copper 2.5 7 House 1980 2400 A/C 10 10 + 10 PVC, Copper 2-5 8 House 1970 1 150 A/C 10 50 PVC 10 9 House 10 House 1 550 A/C 10 400 PVC 5-0 11 House -- -- 12 Office building 1970 250 CPVC 10 5 PVC 1"3 13 Office building 1973 260 CPVC 10 20 PVC 2.5 14 Office building 1974 800 CPVC 10 50 Gav. iron 1-9 15 Office building 1976 600 CPVC 10 20 Copper 2"5 16 Office building 1978 700 CPVC 10 10 Copper 1"3 17 Office building 1983 840 CPVC 10 20 Copper 3-8 18 Office building 1983 1060 CPVC 10 150 + 20 PVC, Copper 5-0 19 School I 1984 350 Gay. iron 7"6 50 Copper 2-5 20 School 1 1984 380 Gay. iron 7-6 50 Copper 2"5 21 School 1 1984 400 Gay. iron 7-6 50 Copper 2"5 22 School 1 1984 400 Gay. iron 7.6 50 Copper 2"5 23 School 2 1984 430 Gay. iron 7-6 50 Copper 2.5 24 School 2 1984 430 Gay. iron 7-6 50 Copper 2"5 25 School 2 1984 430 Gay. iron 7.6 50 Copper 2.5 26 School 3 1984 450 Gay. won 7.6 50 Copper 2:5 27 School 3 1984 450 Gay. iron 7.6 50 Copper 2.5 28 School 3 1984 450 Gay. iron 7-6 50 Copper 2"5 29 Community center 1984 1 520 A/C 10 30 Cafeteria 1974 750 CPVC 10 20 Gay. iron 3.8 31 Cafeteria 1980 250 A/C 10 -- -- 32 Stadium 1980 2100 A/C 10 -- A/C: asbestos/cement; Gay. iron: galvanized iron; CPVC: hard PVC. a Represents pipe length between main line and the point where utilities are connected, i.e. service pipes. residence time for SO samples from these locations was 12 h. The residence time of SO samples from the houses varied between 7 and 9 h. Subsequent water samples from the same points were taken after draining the faucets for 5 and 15 min without allowing the freshwater to stand in contact with the pipes. The second and the third water samples were designated as S 1 and $2, respectively. The groundwater, and the finished or product water samples after all treatments, were collected from the desalination facilities. The collected water samples were divided into two parts: one for pH measurements and the other for metal determinations. The portion for metal determination was preserved using ultrex grade nitric acid. The con- centrations of aluminum, barium, cadmium, chromium, cobalt, copper, 170 lbrahim A. Alam, Muhammad Sadiq calcium, iron, magnesium, manganese, nickel, potassium, lead, sodium, vanadium, titanium, strontium and zinc in the water samples were determined using an inductively coupled argon plasma analyzer (ICAP). The measurements were repeated five times and a mean and standard deviation of these observations were computed. To ensure high quality of the analytical results of this investigation, Standard Reference Material--a water sample (SRM 1643a) obtained from the United States Bureau of Standards (USNBS)--was analyzed along with the collected water samples. RESULTS AND DISCUSSION A comparison of metal concentrations in samples S1 and $2 using a t-test revealed that the chemical compositions of these samples were not significantly different (P < 0"05). Similar concentrations of metals in S1 and $2 samples suggest that freshwater from the mains had reached the sampling points. Therefore, the mean concentrations of metals in the collected water S1 and $2 samples are given in Table 2. Concentrations of metals in SO water samples are also included in Table 2. To evaluate water quality, the maximum permissible and highest desirable concentrations of each metal in drinking water, as suggested by WHO (1971), are given in Table 2. The mean copper concentrations in the S 1 and $2 water samples ranged from below the ICAP detection limit (<0-01) to 3.00#g m1-1. The concentrations of copper in the finished water from the treatment plants and groundwater wells were below the ICAP detection limit. As the drinking water was being transported through the distribution pipes, copper TABLE 2 Mean Metal Concentrations in the Collected Water Samples S. no. Location Sample Metal concentration (#g ml - 1) type Ca Cu Fe K Mg Na Sr Zn pH 1 House S1 +$2 49.66 0-000 0-128 6.86 15.41 183 1.25 0-042 8.07 SO 49.10 0.000 0-090 7.08 15.75 183 1.37 1.000 8.01 2 House S1 +$2 58-66 0.000 0.051 7.39 16.73 184 1.32 0.772 7.96 SO 59.67 0-004 0-102 7.37 17.26 183 1.34 0.723 7.96 3 House SI +$2 22.33 0.000 0-031 4.32 15.71 183 0.52 0.122 7.44 SO 24.60 0.498 0-019 4.36 13.60 183 0.55 1.581 7.89 4 House S1 + $2 39.82 0.042 0-031 6.12 10-99 207 0.88 0-11 7.41 SO 37.29 0.067 1.139 6-88 11.0 202 1.37 2.374 7.73 5 House SI +$2 40.49 0.044 0-034 7.20 11.99 184 0.95 0.025 7.83 SO 58.39 0.908 0"016 7.56 17.23 186 1.39 1.780 7"44 6 House SI +$2 45.75 0.131 0.032 7.53 13.52 183 1.09 0'028 7'26 SO 47.50 1.380 0.007 7.25 18-04 182 1.14 0-356 7.74 Metal contamination of drinking water from pipe corrosion 171 TABLE 2--contd.